1. Field of the Invention
The present invention relates to a member tilting mechanism for use in, for example, a vehicle door or side mirror system and a mirror system incorporating the member tilting mechanism.
2. Description of the Related Art
In general, a tilting mechanism is adopted to be installed in, for example, a vehicle door or side mirror system for tilting a mirror surface vertically and horizontally so as to adjust the mirror surface angularly. This tilting mechanism is normally provided within a mirror housing and is configured as described in, for example, JP-A-2003-194040 (FIGS. 6 and 7). Namely, this tilting mechanism includes, as shown in instant FIG. 10, a housing front 2 that is fixed to a body member (not shown) and is adapted to accommodate therein a motor 1, a housing rear 3 that is covered by the housing front 2, a plate pivot 4 that is mounted on the housing rear 3 and on which a mirror (not shown) is mounted, and a substantially semispherical cap support 5 which holds the plate pivot 4 in such a manner as to be tilted together with the housing rear 3 therebetween.
On the housing rear 3, a concave spherical portion 3a is formed and a cylindrical support tube portion 3b is provided at a center of the concave spherical portion 3a so formed in such manner as to protrude along a central axis thereof. In addition, a convex spherical portion 5a is formed on the cap support 5 along an outer circumference thereof, and a through hole 5b is also formed in the cap support 5 so that the support tube portion 3b can pass therethrough. Furthermore, a pivot portion 4a, which is a tubular portion with an arc-like cross section, is formed on the plate pivot 4 in such a manner as to slide and tilt while being held between the concave spherical portion 3a and the convex spherical portion 5a. 
The support tube portion 3b is put in such a state that the support tube portion 3b is caused to lie or is passed in the through hole 5b in the cap support 5, and a tapping screw 7 is screwed into a mount hole in the support tube portion 3b from an upper end of the support tube portion 3b with a spring plate 6, which is a leaf spring member, placed on the upper end of the support tube portion 3b, whereby the spring plate 6 is fixed in place thereat. The spring plate 6 is formed into a cruciform shape, and a spring center portion 6a is fixed to the support tube portion by means of the tapping screw 7, and distal end portions of deflection portions 6b which extend from the spring center portion 6a radially in four directions are made to press against an outer edge portion of the cap support 5 so that the cap support 5 is pressed towards the housing rear 3. According to this structure, the convex spherical portion 5a is brought into press contact with the pivot portion 4a, which is, in turn, brought into press contact with the concave spherical portion 3a, whereby the convex spherical portion 5a and the pivot portion 4a are allowed to slide relative to the pivot portion 4a and the concave spherical portion 3a, respectively, through such spherical contacts. Consequently, the plate pivot 4 is supported in such a manner as to be tilted in all directions relative to the housing rear 3.
In addition, an adjusting screw 2a is provided in the housing front 2 in such a manner as to protrude therefrom, and an adjusting nut 9 is screwed on the adjusting screw 2a. A worm wheel 10, which is connected to a rotational shaft of the motor 1 and is allowed to move relatively in an axial direction of the rotational shaft, is brought into integral engagement with an outer circumference of the adjusting nut 9 relative to a rotational direction. Furthermore, a spherical joint portion 9a is formed at a distal end portion of the adjusting nut 9, which is then made to fit in a concave joint portion 4b formed in the plate pivot 4 in a press fit state.
Consequently, by driving the motor 1, the adjusting nut 9 moves in the axial direction via the worm wheel 10, so that the plate pivot 4 in which the distal end portion of the adjusting nut 9 is fitted is pushed or pulled, whereby the pivot plate 4 can be electrically tilted together with the mirror. Note that the motor 1, adjusting screw 2a, adjusting nut 9, worm wheel 10 and concave joint portion 4b are each provided in two for vertical and horizontal adjustments.
The related art still has, however, the following problems to be solved.
In the tilting mechanism described in JP-A-2003-194040, when mirrors are replaced at a repair shop or the like, if the mirror is pulled in a direction A indicated in FIG. 10, the plate pivot 4, which is fixed to the mirror, is also pulled in the direction A. While the plate pivot 4 can normally be deflected to a position where a restriction is applied, in the event that the mirror continues to be pulled further in the direction A from that condition, the spring plate 6 is deflected in an opposite direction to the pressing direction (an anti-pressing direction B), whereby the mirror and the plate pivot 4 are deflected excessively, often leading to a problem that the adjusting nut 9 is dislocated from the adjusting screw 2a. 
In addition, while the adjusting nut 9 continues to push the plate pivot 4 until a restriction is applied while being operated electrically, the plate pivot 4 is lifted excessively by such an extent that the spring plate 6 deflects, whereby the plate pivot 4 and the housing rear 3 are made to be separated from each other, often leading to a problem that loosening (beating) occurs in the mirror.
To cope with this, while there is considered a method for making it difficult for the spring plate 6 to be deflected by increasing the spring constant thereof, in this case, the sliding resistance of the pivot portion 4a is also increased, often resulting in a problem that the increase in the sliding resistance inconveniently constitutes a cause for a malfunction.